Electron discharge tube



Dec. 14, 1937. A, T A 2,102,045

ELECTRON DI SCHARGE TUBE F'iled May 15, 1936 3 Sheets-Sheet 1 INVENTO R 3 Sheets-Sheet 2 INVENTOR v WZ% A. G. THOMAS ELECTRON DISCHARGE TUBE Filed May 15, 1936 Dec. 14, 1937.

fly 11 //6 h I I 1/9 A. G THOMAS 2,102,045

ELECTRON DISCHARGE TUBE Filed May 13, 1936 3 Sheets-Sheet 5.

INVENTOR WAWZZM Patented 14, 1937 ATES 3 illia.

. as electron discharge tubes and phototubes which are used in radio, television, and for many other purposes.

An object is to provide a vacuum tube in which the advantages of secondary emission are easily utilized.

Another object is to provide a phototube in which successive reflections from photo-emissive surfaces are employed to increase the electron output.

A further object is to design a phototube combined with light gathering means, to increase the sensitivity of the tube.

An additional object is to design a phototube of many photo-emissive surfaces to increase the output of the tube.

Another object is to provide a self generating phototube, requiring little or no outside source of potential.

A still further object is to provide a combined phototube and filament tube designed so that the photo-emitted electrons will control the filament emitted electrons.

An additional object is to provide a tube in which gaseous ionization can be utilized efliciently.

Other objects I will appear in the following description.

In the drawings:

Figure 1 is an elevation of a filament type vacuum tube with magnetic fields and secondary electron emitting plates.

Figure 2 is an end view of electron-emitting r plates similar to those of Figure 1, and showing the position of one of the permanent magnets used with the tube of Figure 1 to produce the magnetic fields shown in that figure.

. Figure 3 'isan elevation of a phototube using secondary electron-emitting plates, magnetic fields to deflect the electrons, and charged screens to move the electrons toward the anode plate.

Figure 4 is an elevation of'a phototube employing light reflections between photo-emissive surfaces, to increase the electron output.

Figure 5 shows an elevation of a phototube combined with a lens for gathering light.

Figure 6 shows an elevation of a vacuum tube with a photo-emissive cathode, a photo-emissive anode, and a deflecting magnetic field to assist in building up a potential diiference between the cathode and anode.

Figure 7 is a part sectional view of a closed 7 phototube with inner surface coated with photo- (@i. 250-235) This invention relates to vacuum tubes such emissive material. A light gathering lens and an opening for admitting light are shown.

Figure 8 is an elevation oi a phototube with a cathode composed of a plurality of plates.

Figure 9 is an elevation of a phototube with a series of cathodes composed of a plurality of plates.

Figure 10 is a plan view of a filament cathode tube employing phase charging of plates to 1'0- tate electrons and so to produce secondary electrons.

Figure 11 is an elevation of a vacuum tube employing bombardment of a gas by electrons from an auxiliary filament.

Figure 12 is a part-sectional elevation of a vacuum tube with an auxiliary tubular cathode to produce secondary electrons under electronic bombardment.

Figure 13 .is an elevation of a combined filament cathode and photo-emissive cathode tube.

Figure 14 is an elevation of a. vacuum tube employing a deflecting magnetic field and two plates, one of them being grounded.

Figure 15 is an elevation of a vacuum tube with a grounded shield between two plates, one of which is positively charged and the other negatively charged with respect tothe cathode.

Figure 16 is an elevation of a vacuum tube employing a cross stream of electrons to control the main electronic stream.

Figure 17 is an elevation of a filament-oath ode tube employing ionized gaseous conduction between charged plates;

Figure 18 is an end view of a tube with an associated rotatable magnet for deflecting air ions out ofthe tube.

a The various tubes shown, are represented diagrammatically and therefore well known details of construction such as press seals, element supports, and other conventional details will not be described for the most part.

In Figure 1 tube i has filament cathode 2 and plate anode 3. Parallel plates 4 and 5 are supported by rods 6 and I pressed into the cylindrical wall of tube I. The inner surfaces of plates 4 and 5 are coated with some suitable substance such as barium oxide or the like so that several secondary electrons will be emitted from these plates when they are struck by an electron. Magnetic fields 8, 9, ill and H, seen endwise and extending across the cross-sectional area between plates 4 and 5 as shown, are provided. by a series of permanent magnets l2, preferably, placed at .difierent positions along the length of plates 4 and, 5. and positioned as shown in Figure 2. Each succeeding magnetic field is reversed in direction to the field preceding it so that electrons given of! by filament 2- and attracted by plate 3, made positive with respect to filament 2 by battery 13, will be alternately deflected against plate 4 and plate 6 so that the electrons will strike these plates 9. number of times before reaching plate 3. In addition the secondary electrons produced will also be deflected back and forth between plates 4 and 5 so that the effect will be cumulative, with the result that a large current will pass through the output element l4, which may be a transformer or any other suitable device. Battery 15 supplies current for filament 2 and grid l6 may be provided to control the filament produced electrons. Plates 4 and 5 may be grounded to prevent the building up of positive charges on them, if desired.

Filament 2 may be replaced by a photo-emissive cathode instead. Plates l1 and 18, similar to plates 4 and 5, may be provided to catch any stray electrons ejected in an upward or downward direction. Iron plates may be placed between the magnets to act as shields to separate the fields, if desired.

In Figure 3 a similar principle is employed except that electrons are pulled from photoemissive cathode 19 by screens 22, 23, 24 and 25 placed across the cross-sectional area between plates 28a and 29 as shown but insulated from these plates. The negative terminal of battery 21 is connected to cathode l9 and the positive terminal to anode plate 20 and screens 22, 23, 24 and 25 are connected to battery 2| by wires 30, 3|, 32, and 33 respectively, to charge the aforesaid screens at successively higher potentials with respect to cathode 19 so that electrons given off from cathode l9 underinfiuence of light or otherwise, will be attracted by the screens through magnetic fields 26, 21, 28, 29 and 30, produced by magnets I2a, alternately of opposite polarity so that the cathode-emitted electrons as well as secondary electrons will be deflected back and forth from plate 23a to plate 29 and vice versa until all the electrons are finally attracted to plate 20 of highest potential.

Therefore, light falling upon photo-emissive cathode l9 will produce large currents in circuit 34 which may be connected in well known manner to any suitable device. The plates 28a and 29 are coated with a suitable substance for producing secondary electrons under bombardment of primary electrons. Such substances as barium oxide, strontium oxide, etc., are well known for this purpose. Cathode 19 may be coated with a cesiated layer or other well known substance which will eject electrons under influence of light. Filament l9a may also be employed as an additional source of electrons.

It is obvious that either one of the plates 4 or 5 in Figure l or either one of the plates 26a or 29 in Figure 3 may be eliminated since the alternate magnetic fields will cause the electrons to be repeatedly curved against one surface even though the opposing surface is absent. The two surfaces are preferable however since they will produce more secondary electrons than the one surface.

In Figure 4 tube 35 has parallel plates 36 and 31 supported similarly to plates 4 and 5 of Fig-.

plates 36 and 31 are similarly coated. Anodeplate 40 is connected to the positive terminal of battery 41. the negative terminal being connected to cathode 36. Element 42 may be included in the output circuit for any desired purpose. Lens 39 is placed so that it will gather a large amount of light and concentrate it on the inclined faces of cathode 35 so that a large number of electrons will be liberated from this cathode, since the number of electrons emitted is substantially proportional to the intensity of the lightstriking the cathode.

Cathode 36 is also smoothly coated so that it will readily reflect light so that the light rays will bereflected from the inclined faces of wedgeshaped cathode 38 and thence back and forth from plate 36 to 31 and vice versa, each reflection producing additional electrons so that a large number of electrons will finally reach positively charged plate 40. Plates 36 and 31 may be grounded if desired and charged screenssimilar to those of Figure 3 may be employed. These screens themselves may be coated with substances suitable for emitting secondary electrons by electronic bombardment or by the action of light.

A series of alternately oppositely disposed magnetic fields may be used with tube 36 so that the electrons will be deflected back and forth between plates 36 and 31 as well as light, with the result that secondary electrons will be produced by electronic bombardment also. The added effects of the reflected and re-reflected light and the electronic bombardment of plates 36 and 31 will cause a very high output current through element 42. Plates 36 and 31 may be grounded and photo-emissive cathode 46 is placed so that the light concentrated by lens 45 will strike cathode 46 and from there will be reflected successively to electron-emissive and light reflecting plates 41, 43, 49, 50, 51, and 52. Liberated electrons will finally reach anode 53 which is charged positively with respect to cathode 46'by battery 54. Plates 55 and 56 are coated and are provided so that any light or electrons .nissing any of the plates 41, 48, 49, 56. 5i, and 52 will strike one of the plates 55 or 56 and will produce secondary electrons. These two plates are insulated from the other plates which are suitably "connected to a source to be charged by phases so thateach in turn will be successively higher in potential than cathode 46. Such a system of phase charging is described in connection with Figure 10.

In Figure 6 phototube 55 has photo-emissive cathode 56 and photo-emissive anode 51. Metal plate 56 is placed in tube 55 near anode" 51 and is grounded as shown. Magnetic field 60, shown endwise, is provided so that any electrons ejected from anode" 51 will be bent downward to strike grounded plate 58 and electrons ejected from cathode 56, travelling in opposite direction, will be bent upward to strike anode 51. The curvature of cathode 56 may also be arranged so that the electrons which are emitted normally to the surface, will strike anode 51 and this anode may be similarly curved so that electrons, ejected from it will strike plate 58. In either case the electrons from anode 51 will strike grounded plate 89 and will be neutralized or removed from tube 55 so that anode 51 will be left positively charged so that electrons from cathode 58 will be attracted to anode 51 with the result that a current will be indicated by instrument ,99 connected to wires 8i and 62 leading to cathode ,96 and anode II respectively.

Anode 91 may also be illuminated more strongly than cathode 59 to enhance further its positive potential with respect to cathode 99. It. will be seen then that electrons leaving cathode '96 will strike anode 91 but electrons leaving anode ti will not strike cathode 99. The result will be that a current will flow in the outside circuit 92,

93, ti, without an anode battery.

in Figure "l spherical photo-emissive cathode 93 is coated on its inner surface with a cesiated substance or other substance which emits electrons under influence of light. Opening 93 in cathode shell 33 is provided and it is covered by funnel 93' attached to shell 63. Mounted in funnel 35 is lens 93 so that a relatively large amount of light will be collected by this lens and will be directed through opening 64 to strike the inner surface of cathode 99. The light will then be reflected and re-refiected many times so that a large number of electrons will be released from the inner reflecting and electron-emitting surface of cathode t3.

Anode t1 is preferably in the form of a sphere and is supported by wire 12 which passes through insulating plug'lt fixed in shell 93. The positive terminal of battery-69 is connected to spherical anode 9! and the negative terminal to cathode 33, output element ll being included in the circuit. This phototube will, therefore, concentrate a large amount of light in a closed space so that many photo electrons will be liberated to be attracted to anode 61,. A large output current will then be realized. Spherical grid 68 may be provided.

The cathode 63 is shown as a sphere but it can be of any suitable. shape such as a closed cylinder or a cylinder with open ends. In case a cylinder is used, opening 64 should preferably be a rectangular slot parallel to the axis and anode 91 should be an axially placed wire.

In Figure 8 phototube 14 has a photo-emissive cathode consisting of a plurality of parallel plates 15 coated on both faces with a suitable electronemitting substance, the plates being supported and connected together electrically by wire 16 sealed into tube 14. The usual anode l1, battery 19, and output element 19 are provided.

Lenses 80 and ill may be .independently supported or may be combined with tube 1'4 so that light will be directed towards the edges of plates 15 at slight .angle' to cause reflections back and forth from plate to plate. The light may also be directed through plates 15 parallel to the planes of the plates. This multi-surface cathode makes possible a high output of tube 14- with adequate illumination of the cathode.

Cross magnetic fields 15a, 15b, and 150 may be provided to cause the liberated electrons to oscillate between the plates also, thus liberating additional electrons. The cathode '15 may consist of a spiral strip or of a series of concentric circles or surfaces arranged in any convenient way to increase the area. I

In Figure 9 phototube 82 has multi-plate cathode 83 similar to cathode 15 of Figure 8 and similar cathodes 94 and 95 are connected to wires II and 91 respectively. These wires are connected at different points to battery 89. the negative pole of which is connected to cathode 89 and the positive pole of which is connected to anode plate 89. With the connections shown cathode 84 will beat a positive potential with respect to cathode 83 and cathode 85 will be at 'a Positive potential with respect to cathode 9t. and plate anode 89 will be at still higher positive potential. Therefore, light passed through the plates of cathodes 89, 84 and 89 will liberate electrons, and electrons attracted from cathode to cathode will liberatei plied between wires it? and B93 the plates 93,

94, etc., will be charged to maximum potential, respective to filament 9i, in consecutive order so that in effect there will be a rotating field of electrical potential to pull electrons emitted from filament 9i first to plate 93, then to plate 99, and so on to plate 98 and then to plate 93 again so that a large number of secondary-electrons will be released.

Plates 93, 93, etc., are coated with barium oxide, strontium oxide, or with any suitable sub-- stance for liberating secondary electrons under electronic bombardment and the inner surface of tube may likewise be coated. It is assumed of course that the plates are insulated from tube 90 if thatvis conducting. Anode 99 of any suitable shape is provided and screen it, surrounding anode 99, is connected to the negative terminal of battery III), the anode 99 being connected to the positive terminal. The wire ill could be connected to filament 9i and screen illl could be eliminated.

If an alternating potential is placed across the primary I I2 of transformer T and if the secondary is connected in series with battery H9, and if the phase of the extra potential difference across transformer secondary H3 is adjusted so 'the total potential difference between anode 99 and screen Illl is at a maximum when the potential between-filament 9| and any plate 93, etc., is at a minimum, then the cloud of electrons liberated will be periodically drawn to anode 99 "with the result that a current will be set up between collector screen iill and anode 99. The

screen lill may be placed back of plates 93, 94, etc., instead of in front as shown or the screen may be eliminated entirely and wire Ill couldthen be connected to the inner conducting surtrons which are periodically drawn to the anode. A suitable control grid may be provided.

In Figure 11 tube II4 has filament II6 fed by cell H6, and screen H1 is placed at high positive potential relative to filament H6, by battery 8.. Filament H9, grid I20, and plate anode I2I are provided as in the usual three element tube. A certain quantity of gas such as argon or hydrogen is sealed in tube H4 and therefore this gas can be ionized to any degree desired by regulating the current passing through filament H5 and by adjusting the potential difference between filament H5 and screen III, since many of the electrons attracted toward screen II1 will pass through this screen and will strike the gas molecules. The various elements may be connected in any way desired to insure that the electrons from filament II5 will travel the full distance to plate I21 to ionize the whole path of gas. In this way the gas may be ionized to optimum degree so that the output of the tube will be increased. The screen H1 and filament II5 may be replaced by an ultra violet or an X-ray tube.

In Figure 12 tube I22 has filament I23 and screen I24 is positively charged by battery I29 to throw electrons into hollow cylindrical cathode I25 which is coated to produce secondary electrons. Wire coil I26 is wound around cylinder I26 to produce an axial magnetic field so that electrons will be whirled around in cylinder I25 to produce secondary electrons. Plate I21 is made positive with respect to filament I23 by battery I28 so that the primary and secondary electrons will finally reach plate I21. Grid I28a may be provided. 7

In Figure 13 tube I30 has filament cathode I3I, grid I31, and plate anode I36. Photo-emissive cathode I is also provided and it is made negative with respect to grid I31 by cell I36 although this cell is not essential since cathode I35 may be so curved and so placed that it will 'eject electrons upon grid I31 when the cathode I35 is struck by light. Now filament I3I fed by cell I32; grid I31; plate I38; and plate battery I33; connected as shown constitute a usual three electrode tube but the addition of photo-emissive cathode I35 makes it possible to control the filament-plate current by means of light. Shield I34 may be employed to prevent light from filament I3I from acting upon cathode I35 and it may also serve to separate the electrical fields. This shield may be grounded if desired.

Since grid I31 is slightly positive with respect to cathode I35 it will be seen that the grid will accumulate electrons in proportion to the degree of illumination of the cathode I35 and grid I31 will in turn control the tube current from filament I3I to plate I33. Battery cell I36 may be eliminated and also a suitable grid leak may be employed to prevent too great an accumulation of negative charge on grid I31. The upper part of grid I31 may be a solid plate to receive more electrons from cathode I35.

In Figure 14 tube I39 has filament I40, grid I4l, plate I42, and auxiliary plate I43 placed as shown and grounded. Magnetic field I44, seen endwise, is provided so that negative electrons liberated from filament I40 or from gas in tube I39 will be deflected upward to plate I42 but positive gasions will be deflected downward to strike against grounded plate I43 and so will become neutralized. Grid I4I controls the current as usual. A series of grounded plates I43 placed at strategic points may be used.

This tube then will make possible the use of high gaseous ionization produced from electronic bombardment or otherwise with resulting increased currents since the erratic gaseous ions are deflected from the main current stream. A

suitable gas would be hydrogen, which produces.

positively charged ions.

In Figure 15 a similar principle to that employed in the tube illustrated in Figure 1a is used. Tube I45 has filament I46 fed by battery I55. The negative terminal of plate battery I52 is connected to filament I46 through output element I64 and the positive terminal is connected to plate I49. The negative terminal of battery charged by battery I53, with respect to filament I46, so that the positive ions will be electrostatically attracted to plate I and so will be removed from the main current stream. Shield I5I may be eliminated if desired. Cathode grid I41 may be so placed that most of the positive ions produced by electronic bombardment will be defiected from grid I41 and so will not strike it.

This tube then will carry large currents with more stability than the usual form of tube containing an ionizable gas. A gas such as hydrogen may be introduced in proper amount into tube I45.

In Figurel6 tubev I56 is in the shape of a cross as shown and contains filament cathode I51 and anode I58. An additional filament I59 and plate anode I60 are placed perpendicularly as shown so that the electronic stream passing from cathode I59 to anode I60 will 'create a negatively charged electron cloud to control the stream of electrons passing from filament I51 to anode I59, suitable charging batteries being provided. Grid I6l may be employed to control the electron stream from cathode I59 to anode I60. Likewise cathode I59 may be a photo-emissive plate so that the current between cathode I51 and anode I53 may be controlled by light. In this way the main current stream is unobstructed by solid objects such as grids.

In Figure 17 tube I62 has filament cathode I63 and anode I64 is positively charged with respect to cathode I63 as usual. Metal plate electrodes I and I66 are connected to battery I61 with output device I63 in series. A certain amount of gas is introduced into tube I62-so that it will become ionized by the electrons passing from cathode I63 to anode I 64 so that the path between electrodes I 65 and I66 will become more conducting. This tube will then make an efiec- -tive relay. A grid may also be used in front of filament I63 and this element may be a photoemissive cathode instead of a filament.

In Figure 18 a method of evacuating tubes is illustrated. Air is pumped from tube I69 through small connecting tube I10 which may be sealed oil when the proper degree of vacuum is reached. In order to assist in removing the air, horseshoe magnet I16 is provided. This magnet has fastened to it shafts I13 and I14 which may be rotated at high speed in suitable bearings. Pulley I15, fastened to shaft I 14, serves to rotate the shafts and magnet I16 so that the magnetic field between poles I'll and H2 will be swept across tube I69 periodically at high speed to defiect any charged air ions out through tube I10. These ions may be produced by electronic bombardment within the tube I69, or by ultraviolet or X-ray radiation. Since there will usually be both positive and negative ions magnet I18 should be rotated for a while in one direction and then for a period in the reverse direction so that practically all gaseous ions will be deflected through tube I10 to which an evacuating pump will be connected as usual. Electrode ll! of wire screening or, otherwise may be connected to wire H8 charged positively for a period and then negatively, with respect to the elements in tube I69 so that the air ions will also be removed electrostatically. The sign of the charge on screen I'll should be such that it will assist the magnetic-deflecting action.

If the tube I69 has a metal shell a high potential difference may be maintained between filament I19 and shell I69 or between filament I19 and grid I80 or between any two so that the remaining air molecules will become ionized by electronic bombardment, or as stated, X-rays can be directed vthrough the air in the tube to cause the ionization.

A series of magnets similar to magnet I'IB may be rotated or a rotating magnetic field pro-' duced by suitably placed coils with currents out of phase may be employed to deflect the gaseous ions out of the tube.

This method furnishes a very eflfective means for producing very high vacua in tubes.

Many possible combinations of the various elements shown are possible without departing from V the spirit of my invention.

What I claim is:

1. A vacuum tube comprising a cathode, an anode, a pair of opposed surfaces on either side of the normal electron pathfrom said cathode to said anode for producing secondary electrons and means for producing a plurality of magnetic fields of alternately opposite polarity spaced between said surfaces at intervals for deflecting electrons emitted by said cathode from surface to surface along with secondary electrons to produce a relatively large number of electrons finally reaching said anode.

.2. A vacuum tube comprising, a cathode, an anode, a pair of opposed surfaces on either side of the normal electron path from said cathode to said anode for producing secondary electrons, a plurality of electrically conducting members positioned between said surfaces at intervals, and means for producing a plurality of magnetic fields of alternately opposite polarity between' said surfaces to deflect electrons from surface to surface to liberate secondary electrons from said surfaces.

will be repeatedly directed against said surface to liberate additional electrons.

ALBERT G. THOMAS. 

